This invention relates to a process for degrading of textiles comprizing polyester fiber and/or acetate fiber.
By degrading is meant to process these textiles with an aqueous solution containing alkaline substance so as to chemically decompose a part thereof and remove it from the textiles. In the degrading of textiles comprizing polyester fiber, a part of polyester is hydrolyzed into ethylene glycol and terephthalic acid and removed from textiles. In the degrading of the textiles comprizing acetate fiber, a part of acetyl group of cellulose acetate is hydrolyzed and removed.
Degrading of textiles comprizing polyester fiber has widely been practiced (refer to British Patent Specification No. 786153). On the other hand, degrading of textiles comprizing acetate fiber has not been practiced industrially as yet, but it is attracting interest as one means for processing the textiles. By degrading the textiles comprising polyester fiber, textiles can be obtained which have softness similar to silk, and reduced tendency for generating static electricity, and which are excellent in prevention of pilling, and in stainproofing property, etc. Furthermore, when degrading is applied on textiles comprizing acetate fiber, the surface of the acetate fiber is changed to cellulose, i.e., a fiber of double construction, having acetate in the interior, and cellulose in the surface, is obtained, and it is considered that the feeling thereof is improved.
The degree of improvement obtained by degradation depends on the rate of degradation, that is to say, the rate of decrease of weight of the textiles by degradation.
Problems on practicing the degrading industrially are that it is difficult to control the rate of degradation at high accuracy, and some times textiles are obtained to which excessive degradation have been proceeded, or to which the predetermined rate of degradation has not been attained. For example, in the degrading of textiles comprizing polyester fiber, a method is carried out in which several pieces of test cloths of known weight having the same quality as the textiles are attached to the textiles to be treated, and when the degradation seems almost to comes to its finishing point, the test cloths are taken out one by one, and by measuring the decrease of their weight, it is possible to determine whether or not the textiles under treatment reached to the predetermined rate of degradation. However, the degrading of textiles under treatment proceeds even while the test cloths were taken out and the weight were measured, so that it is difficult to control the rate of degradation with good accuracy by this method. In another method, previously drawing experimentally a diagram showing relations between the concentration of the "solution" (in the specification and Claim, it is referred to as "treating bath") containing basic substance used for degrading, degrading temperature, processing time and rate of degradation and by use of the diagram, the time reaching the desired rate of degradation can be estimated. However, with this method, again, it is not always possible to obtain textiles having desired rate of degradation, because strict control of concentration or temperature of the treating bath is difficult.